Gas expansion apparatus for a system for the conversion of thermal energy into motive energy, in particular for a hot-water motor

ABSTRACT

The invention relates to a gas expansion apparatus which is part of a system for the conversion of thermal energy into motor energy, especially for a hot-water motor.

BACKGROUND OF THE INVENTION

The invention relates to a gas expansion apparatus which is part of asystem for the conversion of thermal energy into motive energy, inparticular for a hot-water motor, consisting of a closed pressure vesselwhich is filled with a gas or a gas mixture, which is operativelyconnected to the system via a displaceable piston (liquid displacementpump) and which has at least one upper injection orifice for hot and forcold water and a lower water outflow orifice (liquid outflow pipe).

Gases, when heated and expanded, convert a relatively large amount ofheat into work, thus giving rise, in rapid processes, such as, forexample, the Stirling process, to major losses due to dissipation,unfavorable piston control, heat and hunting losses, clearance volumeeffects, high regenerator resistance and high velocities.

U.S. Pat. No. 4,283,915 discloses a arrangement for the conversion ofthermal energy into motive energy, which in each case comprises a feedfor hot water and a feed for cold water, a specific temperaturedifference prevailing between the hot water and the cold water. The hotwater and the cold water are conducted alternately through tubes of aheat exchanger, in order to expand and contract a working liquid. Thework cycle is carried out below a boiling point of the working liquid.Nonreturn valves ensure a relatively high pressure for the actuation ofthe arrangement. In this case, the use of the heat exchanger proves tobe a disadvantage, since such a tube heat exchanger, which involves ahigh technical outlay, has only greatly limited efficiency and,depending on the nature of the media flowing through and around it, isrelatively susceptible to faults.

Moreover, DE 197 19 190 C2 discloses an arrangement for the conversionof thermal energy into electrical energy, which consists of a workingcircuit with a working fluid for driving a turbomachine and of amultiplicity of heat exchangers through which a cold medium and a hotmedium flow alternately. In each of the heat exchangers is arranged anexpansion element which expands and contracts as a function of thetemperature of the medium and the temperature-induced expansions andcontractions of which are supplied to the working circuit via a bufferstore. For storing a force, each heat exchanger is assigned a bufferstore designed as a spring, each spring being connected to the piston ofa pressure cylinder, the working space of which is connected in eachcase by control valves, via suction and delivery lines, to a working oilcircuit which drives a turbine having a generator. This arrangement hasa relatively complex set-up, in particular because of the buffer storesdesigned as springs, and suffers from the disadvantages of a heatexchanger which were explained above.

Furthermore, EP 0 043 879 A1 discloses a gas expansion element, designedas a cylinder, for the conversion of thermal energy into motive energy.For the operative connection of the cylinder to the arrangement, apiston is mounted displaceably in the cylinder filled with air. Thecylinder has an upper injection orifice for hot water and a controllablelower water outflow orifice.

SUMMARY OF THE INVENTION

The object of the invention is to provide a gas expansion apparatus ofthe type initially mentioned, by means of which a relatively high poweroutput can be achieved at a low, technical outlay.

The object is achieved, according to the invention, in that

the pressure vessel has an upper injection orifice for cold water,

the lower water outflow orifice is arranged at the lower end of a sumpwhich projects downward beyond the pressure vessel and which has asubstantially smaller diameter than the pressure vessel, and

the piston is designed as a liquid piston pump (liquid displacementpump) which is connected on the inlet side to the water outflow orificeof the pressure vessel, said orifice being assigned a water inflow of aworking circuit, and on the outlet side to a water outflow of theworking circuit.

These measures ensure that expansion and contraction of the same medium(gas) takes place into one and the same chamber of the gas expansionapparatus, with the result that the gas expansion apparatus is producedat a low technical outlay. The medium contracting during the supply ofcold water and expanding during the supply of hot water therefore actsupon the piston designed as a liquid piston pump, without losses of aheat exchanger or the like occurring. At the same time, in order to heatthe air or another gas in the pressure vessel, hot water is sprayeddirectly into the pressure vessel where it as far as possibleimmediately penetrates a gas to be expanded. The condensate is collectedin the sump which prevents the gaseous medium from flowing out of theinterior of the pressure vessel. Due to the relatively small diameter ofthe sump, with the latter at the same time having a relatively longlength, the heat transmission between the interior of the pressurevessel and an outflow for the condensate or the outflowing condensateitself is reduced. Furthermore, the liquid piston pump is not subject toany frictional losses, with the result that the efficiency is increased,as compared with the use of a piston guided in a cylinder.

According to an advantageous embodiment of the invention, an injectionorifice with a spray and atomizer nozzle directed into the interior ofthe pressure vessel is provided in each case for the hot water and thecold water. The spray and atomizer nozzle brings about a finedistribution of the injected hot or cold water in the pressure vesseland therefore a rapid penetration of the gas. Furthermore, the separateinjection orifices having the associated atomizer nozzles ensure that,when cold water is injected, no residues of hot water enter the interiorof the pressure vessel and, conversely, also no residues of cold waterare introduced when hot water is being injected.

In order largely to prevent heat losses, preferably at least the innerwall of the pressure vessel consists of a material not absorbing heat oris coated with an insulating material.

For the relatively rapid downward discharge of the hot or cold waterinjected into the pressure vessel, expediently the inner wall of thepressure vessel consists of a water-repelling material or is coated withsuch a material.

For controlling the injection time of the hot or cold water, expedientlythe liquid piston pump is provided in each case with a level sensor foran upper and a lower level of the water within the liquid piston pump.After the upper level is reached, the injection of the hot water intothe pressure vessel takes place by computer control, whereupon thegaseous medium in the pressure vessel expands and the level of the waterwithin the liquid piston pump falls until the lower level is reached andthe associated level sensor, by computer control, signals the injectionof cold water for the contraction of the gaseous medium.

To prevent an undesirable pressure drop and to preset the direction offlow in the working circuit, preferably a nonreturn valve is inserted ineach case into the water outflow and the water inflow.

Advantageously, the pressure vessel is designed to merge in afunnel-shaped manner in the sump or in the direction of the wateroutflow. This shape is conducive to a rapid downward discharge of theinjected hot or cold water.

It goes without saying that the features mentioned above and those stillto be explained below can be used not only in the combination specifiedin each case, but also in other combinations, without departing from thescope of the present invention.

The gas expansion apparatus presented in this application for letterspatent comprises a gas expansion apparatus including a closed hollowpressure vessel, a liquid displacement pump having a gas/liquidinterface, and a working circuit. An injection nozzle is located at anupper end of the pressure vessel for injection of a first liquid and ofa second liquid into the pressure vessel, the first liquid being at ahigher temperature than the second liquid. A sump is located at a lowerend of the pressure vessel, and the sump has a substantially smallerdiameter than the diameter of the pressure vessel and projects downwardfrom the pressure vessel. A controllable liquid outflow pipe is locatedat the lower end of the sump. A liquid displacement pump has agas/liquid interface and an inlet and an outlet; the inlet of the pumpis connected to the controllable liquid outflow pipe. The workingcircuit drives a thermal energy conversion device, and has a liquidinflow connected between the controllable liquid outflow pipe and thethermal energy conversion device; the working circuit also has a liquidoutflow connected between the outlet of the pump and the thermal energyconversion device. Injection of the first liquid into the pressurevessel causes gas contained within the pressure vessel to expand,driving the gas/liquid interface of the pump in a first direction toincrease pressure on the liquid in the working circuit; the pressure onthe liquid in the working circuit drives the thermal energy conversiondevice. Injection of the second liquid into the pressure vessel causesthe gas contained within the pressure vessel to contract, displacing thegas/liquid interface in a second direction opposite to the firstdirection.

The injection nozzle may be a spray and atomizer nozzle. The inner wallof the pressure vessel may comprise a material that does not absorb heator a coating of insulating material. The inner wall of the pressurevessel may comprise a liquid-repelling material or a coating ofliquid-repelling material. The liquid piston pump may be provided withlevel sensors for detecting a lower level of liquid at a lower endposition within the liquid displacement pump and for detecting an upperlevel of liquid at an upper end position within the liquid displacementpump. A first working circuit nonreturn valve may be located within theliquid outflow of the working circuit and a second working circuitnonreturn valve may be located within the liquid inflow of the workingcircuit. The lower portion of the pressure vessel may have the form of afunnel such that it merges into the sump.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below by means of twoexemplary embodiments, with reference to the accompanying drawings inwhich:

FIG. 1 shows a section through a gas expansion apparatus according tothe invention, with associated components, and

FIG. 2 shows an alternative version of the gas expansion apparatusaccording to FIG. 1.

An essentially cylindrical to spherical pressure vessel 1 according toFIG. 1 has, on its top side, an injection orifice 2 which has a sprayand atomizer nozzle 3 directed into the interior of the pressure vessel.Hot water or cold water can be injected alternately into the pressurevessel 1 via associated valves 4 and 4′. A liquid other than water canbe used as well.

DETAILED DESCRIPTION OF THE INVENTION

The pressure vessel 1 filled with a gas or a gas mixture is connected inits wall to a displaceable piston 5 which makes the connection to anarrangement 9 for the conversion of motion of the piston to motiveenergy at a location different from the location of said piston. Thesystem illustrated in FIG. 1 could function as a hot water motor.

The pressure vessel 1 is of funnel-shaped design at its lower portion 6which merges in a sump 7 which projects downward beyond the pressurevessel 1 and which has a controllable lower water outflow orifice 8 atits lower end.

In order to heat the air or other gases of the pressure vessel 1, hotwater is injected directly by way of the associated valve 4 and theinjection orifice 2, via the spray nozzle 3, into the pressure vesselwhere it largely immediately penetrates the gas to be expanded. Thepressure vessel 1 is insulated at least on the inside, otherwise overits entire wall, in such a way that it does not absorb any heat in thematerial. Moreover, the inner wall is water-repelling, in order todischarge the introduced water rapidly downward after cooling.

The air heats up with the injection of the hot water, expands and, viathe displaceable piston 5, performs work which is supplied to a workingcircuit 20, not illustrated in any more detail, of the arrangement 9 forthe conversion of the thermal energy. The spraying of the hot watertakes place, in this case, in such a way that the heat or cold carriedin the water can spread out immediately in the vessel. This ensures ahigh clock frequency (approximately one cyclic process in one to threeseconds).

After the pressure rise and, after piston displacement, thecorresponding pressure drop in the pressure vessel, and aftercorresponding cooling, the water falls out and settles downward in thesump 7. The controllable lower water outflow orifice 8, by computercontrol, discharges there only so much water that the sump 7 isprevented from becoming dry and, consequently, an outflow of gas/air isavoided. The sump 7 is kept long and narrow, so that no heattransmission into the outflowing water can take place.

The quantity of water required for heating is very small. Thus, 9.1 kJin 22 g of water is sufficient for heating 100 liters of air from 0° C.to 100° C. In this case, a useful work of 3.6 kJ becomes available(approximately 40% efficiency when air is used).

For the cooling and subsequent contraction of the air (gas) in thepressure vessel 1, cold water is injected. A negative pressure isgenerated, so that the displaceable piston 5 returns to the initialposition again. The efficiency can be increased by means of specialgases or gas mixtures.

The valves 4 and 4′ are assigned to the pressure vessel 1 according toFIG. 2 on its top side, one valve 4′ being coupled via a connecting line10′ to a cooling device 11 for generating the cold water and the othervalve 4 being coupled likewise via a connecting line 10 to a heatingdevice 12 for generating the hot water. The hot water enters aninjection orifice 2, which has an associated spray and atomizer nozzle3. Similarly, the cold water enters an injection orifice 2′, which hasan associated spray and atomizer nozzle 3′.

The cooling device 11 and the heating device 12 are fed by a pump 14 viaan appropriately branching line 13, the line 13 being connected to acompensating vessel 15. A nonreturn valve 27 is inserted into the line13 directly upstream of the cooling device 11, and a nonreturn valve 26is inserted into the line 13 directly upstream of the heating device 12.The nonreturn valves 27 and 26 prevent the appropriately thermallycontrolled water from flowing out of the cooling device 11 and out ofthe heating device 12. Furthermore, a nonreturn valve 25 is provided inline 13 between the pump 14 and an inflow 32 of the compensating vessel15. In order to fill the entire system with water, the compensatingvessel 15 is connected to a corresponding water supply via an inflowvalve 30. Moreover, the compensating vessel 15 is coupled to the pump 14via a pressure sensor 31.

Arranged on the underside of the pressure vessel 1, below the sump 7,according to FIG. 2 is a liquid piston pump 17 which is filled withwater 16 and which is connected on the inlet side to the water outfloworifice 8 of the pressure vessel 1, said orifice being coupled to awater inflow 23 of the working circuit 20, and on the outlet side to awater outflow 33 of the working circuit 20. During the expansion of thegaseous medium in the interior of the pressure vessel 1, that is to sayduring the injection of hot water, the water 16 is subjected to pressurecorrespondingly in the liquid piston pump 17 and the level 18 assumes alower end position monitored by a level sensor 29 which controls the endof the injection phase of the hot water. In this case, a first workingcircuit nonreturn valve 19 assigned to the water outflow orifice 8 isopened, and the generated pressure is propagated in the water circuit 20in the direction of the arrow 21. During the build-up of pressure in theworking circuit 20, a second working circuit nonreturn valve 22 in awater inflow 23 arranged between the pressure vessel 1 and the liquidpiston pump 17 is closed, said nonreturn valve being opened at a latertime, to be precise during the contraction of the gaseous medium in theinterior of the pressure vessel 1, in order to feed the medium 16 intothe liquid piston pump 17 and to form the working circuit 20.

During the contraction of the gaseous medium in the interior of thepressure vessel 1 as a result of the injection of cold water, thenonreturn valve 19 assigned to the water outflow orifice 8 is closed,and the level 18 of the medium 16 of the liquid piston pump 17 assumesan upper end position which is likewise monitored by a level sensor 28.After a corresponding signal has been given by the level sensor 28, theinjection phase of the cold water is terminated.

During the flow through the working circuit 20, the water 16 drives thearrangement 9, connected into the working circuit 20, for the conversionof the thermal energy. Liquid media other than water 16 may, of course,also be used for operating the working circuit 20.

The condensate or outflowing water occurring in the pressure vesselarrives, via the liquid piston pump 17, at the working circuit 20 whichis coupled to the pump 14 which, in turn, by means of correspondingcontrol by the pressure sensor 31 of the compensating vessel 15,supplies the outflowing water to the cooling device 11, the heatingdevice 12 and the compensating vessel 15.

To control the sequences, the valves 4, the level sensors 28 and 29 ofthe liquid piston pump 17, the pressure sensor 31 of the compensatingvessel 15 and/or the pump 14 may be coupled to a computer, notillustrated, which monitors the injection operations, the level 18 andthe pressure and correspondingly activates the components listed above.

What is claimed is:
 1. A gas expansion apparatus, comprising: a closedhollow pressure vessel including an injection nozzle located at an upperend of said pressure vessel for injection of a first liquid and of asecond liquid into said pressure vessel, said first liquid being at ahigher temperature than said second liquid; a sump located at a lowerend of said pressure vessel, said sump having a substantially smallerdiameter than that of said pressure vessel and projecting downwardtherefrom; a controllable liquid outflow pipe located at said lower endof said sump; a liquid displacement pump having a gas/liquid interfaceand an inlet and an outlet, said inlet of said pump being connected tosaid controllable liquid outflow pipe; and, a working circuit fordriving a thermal energy conversion device, said working circuit havinga liquid inflow connected between said controllable liquid outflow pipeand said thermal energy conversion device, and said working circuithaving a liquid outflow connected between said outlet of said pump andsaid thermal energy conversion device, whereby injection of said firstliquid into said pressure vessel causes gas contained within saidpressure vessel to expand, driving the gas/liquid interface of said pumpin a first direction to increase pressure on liquid in said workingcircuit, thereby driving said thermal energy conversion device, andinjection of said second liquid into said pressure vessel causes the gascontained within said pressure vessel to contract, displacing saidgas/liquid interface in a second direction opposite to said firstdirection.
 2. The gas expansion apparatus of claim 1, wherein saidinjection nozzle comprises a spray and atomizer nozzle.
 3. The gasexpansion apparatus of claim 1, wherein an inner wall of said pressurevessel comprises at least one of a material that does not absorb heatand a coating of insulating material.
 4. The apparatus of claim 1,wherein said inner wall of said pressure vessel comprises at least oneof a liquid-repelling material and a coating of liquid-repellingmaterial.
 5. The apparatus of claim 1, said liquid displacement pumpprovided with level sensors for detecting a lower level of liquid at alower end position with said liquid displacement pump and for detectingan upper level of liquid at an upper end position within said liquiddisplacement pump.
 6. The apparatus of claim 1, further comprising: afirst working circuit nonreturn valve located within said workingcircuit liquid outflow; and, a second working circuit nonreturn valvelocated within said working circuit liquid inflow.
 7. The apparatus ofclaim 1, said pressure vessel having a lower portion in form of a funnelwhich merges into said sump.